diff --git a/CHANGES.rst b/CHANGES.rst
index ce3114e28..112d072a0 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,6 +1,16 @@
 Release Notes
 =============
 
+2.1.126
+-------
+
+This release fixes a long standing (> 4 years old!) concurrency bug
+when building the same sdist for the 1st time and racing another Pex
+process doing the same sdist build.
+
+* Guard against racing sdist builds. (#2080)
+  `PR #2080 <https://github.com/pantsbuild/pex/pull/2080>`_
+
 2.1.125
 -------
 
diff --git a/pex/version.py b/pex/version.py
index cafa484de..014827637 100644
--- a/pex/version.py
+++ b/pex/version.py
@@ -1,4 +1,4 @@
 # Copyright 2015 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-__version__ = "2.1.125"
+__version__ = "2.1.126"